Compilare: user.c: In function ‘fib’: user.c:10:5: warning: implicit declaration of function ‘power’ [-Wimplicit-function-declaration] power(F, n-1); ^ user.c: At top level: user.c:14:6: warning: conflicting types for ‘power’ [enabled by default] void power(long long F[2][2], int n){ ^ user.c:10:5: note: previous implicit declaration of ‘power’ was here power(F, n-1); ^ user.c: In function ‘power’: user.c:18:9: warning: implicit declaration of function ‘multiply’ [-Wimplicit-function-declaration] multiply(F, F); ^ user.c: At top level: user.c:25:6: warning: conflicting types for ‘multiply’ [enabled by default] void multiply(long long F[2][2], long long M[2][2]){ ^ user.c:18:9: note: previous implicit declaration of ‘multiply’ was here multiply(F, F); ^ user.c: In function ‘main’: user.c:46:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d", &k); ^